Power generation systems often include a power converter that is configured to convert an input power into a suitable power for application to a load, such as a generator, motor, electrical grid, or other suitable load. For instance, a power generation system, such as a wind turbine system, may include a power converter for converting variable frequency alternating current power generated at the generator into alternating current power at a grid frequency (e.g. 50 Hz or 60 Hz) for application to a utility grid. An exemplary power generation system may generate AC power using a wind-driven doubly fed induction generator (DFIG). A power converter can regulate the flow of electrical power between the DFIG and the grid.
In many instances, power generation systems may be located in remote areas far from the loads they serve. This is particularly true for renewable energy sources, such as wind turbine systems, solar/photovoltaic systems, hydroelectric systems and/or the like. Typically, such power generation systems are connected to the electrical grid through an electrical system including long transmission lines connected to the grid using one or more breakers.
As is generally understood, a grid fault may occur within or along the electrical system connecting a power generation system to the grid, which may result in a transient event (e.g., a high voltage event, a low voltage event or a zero voltage events) that can detrimentally impact the various components of the power generation system unless a suitable corrective action is taken. In some instances, some types of grid fault may result in the opening of a protective breaker upstream of the power generation system such that the system experiences the opening of one or more phase conductors of the electrical system, thereby causing an islanding event for the power generation system. Unfortunately, islanding events resulting from the sudden tripping of a transmission line breaker at the grid side while the power generation system is under load may result in an overvoltage on the transmission line that can lead to damage to the one or more components of the power generation system, particularly the power converter and its related components or up-tower components. Some of this damage can also result in an in-proper shutdown of the equipment after the islanding event.
Typically, the corrective action required in response to an islanding event is a complete shutdown of the power generation system. However, if the generator is tripped prior to the breakers and/or the contactors of the power generation system being opened, a significant amount of damage may occur to one or more of the system components due to the grid shunt capacitance remaining on the isolated grid. Thus, it is often desirable to temporarily maintain operation of the system until it can be ensured that the proper breakers and/or contactors are open. Unfortunately, due to the unique operating parameters associated with an islanding event, conventional control methodologies are not adapted to properly control the power converter and other electrical components of the power generation system in a manner that allows for a safe and efficient shut down of the system.
Accordingly, an improved system and method for controlling aspects of the operation of a power generation system that allow for the system to be safely and efficiently shut down in response to the detection of an islanding event would be welcomed in the technology.